125Aging of polymers is a combination of physical and chemical processes occurring during storage, process ing, and exploitation of polymeric materials and resulting in a change in their properties [1]. Depend ing on which processes prevail, chemical and physical aging of polymers can be distinguished. Under the action of oxygen, ozone, high temperature, light, pen etrating radiation, mechanical stress, etc., degradation processes may occur in polymers; they entail decom position of polymer chains and lead to formation of low molecular mass products. The improvement of known polymers and the creation of polymeric mate rials with new valuable properties are based on achievements in the chemical physics of aging and sta bilization of polymers [2,3]. However, owing to the thermodynamically nonequilibrium structure of poly mers (even in the absence of chemical transforma tions), relaxation processes occur in them; as a result, the polymers tend toward the state close to equilib rium. This process is referred to as "physical aging" [4] and is accompanied by change in local supramolecular structures [5]. Various factors responsible for aging of materials act both individually and jointly [6].Investigations of physical aging have been per formed for a very large amount of amorphous and semicrystalline polymers, and the main publications in this field concern the study of their nonequilibrium glassy states [7][8][9][10][11][12][13][14][15][16][17]. It is shown that the time and ther mal prehistory strongly affect the physical aging of polymeric materials [3,13,18,19]. Evidently, almost all composite materials are subjected to aging; how ever, little is known about the effect of physical aging on the properties of multicomponent heterogeneous systems. For example, it has been found that the pres ence of a filler in the polyvinylbutyral matrix during aging may initiate crosslinking processes in the system [20]. Thus, in manganese containing segmented poly urethanes, the redistribution of coordination bonds occurs during physical aging [21]. For compatible blends of atactic poly(methyl methacrylate) and sta tistical styrene-acrylonitrile copolymers, the rate of volume relaxation depends on the aging temperature and blend composition [22].For heterogeneous systems, such as interpenetrat ing polymer networks (IPNs), physical aging pro cesses possess their own specifics related to phase sep aration; that is, they occur independently in each phase and have different times [23][24][25]. As was shown in [25], during aging of semi interpenetrating polymer networks (semi IPNs) based on network PU and lin ear PS, there are structural and phase transformations that are related to an increase in the amount of topo logical entanglements in the system due to of fluctua tions of polymer chains and redistribution of segmen tal mobility with a change in the rate of relaxation pro cesses of each phase. Since the main factors of physical aging are by determined by relaxation pro cesses occurring in the system, which in turn depend on its str...
